The dynamic speckle phenomena have been studied using photon correlation methods when laser light with Gaussian intensity profile and a curved wavefront illuminates a rotating diffuser. In this photon correlation experiment we have determined that photon correlation function $g^(2)$ (0,0) which is dependent on the distance of the diffuser from the focal point. When the distance is increased to satisfy the Central Limit Theorem, we obtain the result that the photon correlation function have Gaussian statistical property as $g^(2)$ (0,0) approached to 2.
Also, the laser beam size is measured using spatial photon fluctuation correlation funtion at the Gaussian statistical limit. The velocity of a moving diffuser is also determined by using temporal photon correlation function by varing the power voltage of the motor.
